Gas turbine engines may comprise a gear train in the torque transfer path from a turbine to a compressor and/or fan. Where the gas turbine engine is arranged to provide a large amount of power, the gear train may have a large diameter to withstand the relatively high torque transferred from the turbine. However, a large diameter may result in the gear train being subjected to large centrifugal forces (due to rotation of the planet gears for example) which may cause wear and subsequent failure of the gear train. The requirement for a large diameter gearbox may also lead to design compromises in other aspects of the engine such as restriction of the main gas path and increased weight.